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VOLUME -23 NUMBER 3
Publication Date: 03/1/2008
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Special Feature: PCB and Assembly
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March 2008 Issue
Special Feature: PCB and Assembly
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Budget Priced Systems Meet Small Shop Needs
New convection reflow soldering system for small to medium-sized production lines.
By Heike Schlessmann, Marketing Manager, SEHO Systems GmbH, Kreuzwertheim, Germany
In spite of the relentless drive toward miniaturization and the increased use of reflow soldering for SMT, there has continued to be a need for wave soldering, even though this process has steadily lost ground to reflow. Continuing miniaturization of products has been the driving force behind this trend; more and more functions are integrated into smaller assemblies.
This trend is exemplified by the onslaught of the burgeoning mobile phone market, new levels of automotive electronics, safety technology, and control technique. Reflow soldered components tend to be tiny, allowing increased flexibility and freedom of design, and they may be placed much more closely than components that have leads or "tails". However, not all components are available as SMDs, or they are much more expensive than corresponding leaded components.
Typically, these very few conventional components are manually soldered into place after the reflow process. But due to the intensified pressure to improve product quality, to shorten cycle times, and to reduce non-controllable variables as well as product cost, many manufacturing operations can no longer tolerate hand soldering.
Because of this, it makes sense to integrate a selective soldering system into the production line
the reflow process in the majority of applications. This allows economical soldering of remaining leaded components and this more readily accommodates lead-free processes.
At first blush, this might sound like a huge investment, but this is not the case. The new "Go" product line from SEHO includes high precision automatic soldering systems for both reflow and selective soldering applications — particularly for small and medium-sized production operations, and at an affordable price. An immediate benefit: the quality of the manufactured products will be improved and most expensive manual rework will be avoided.
Powerful Convection Reflow
With a heating zone length of 72.8-in. or 92.5-in. the convection reflow soldering systems GoReflow 1.8 and GoReflow 2.3 are especially suited for small-to-medium-size production lines. The GoReflow 1.8 has 5 heating zones and the GoReflow 2.3 has 7 to provide maximum flexibility in temperature profiling. This allows precise processing parameters for all material- and process-related variables, particularly for lead-free soldering process.
Environment-friendly process gas cleaning.
The GoReflow systems are designed for soldering in normal atmosphere. A high volume of circulated process gas, which is generated with axial fans, and especially adapted slot nozzles, ensure a very homogeneous heat distribution over the complete transport width at moderate gas velocities. This way, a very good heat transfer rate to the assemblies is realized so that the set temperatures of the oven can remain on a lower level. This goes a long way toward fulfilling today's requirements for the narrow process window of the lead-free soldering process: all the components will be soldered while the temperature impact on the components is significantly reduced.
Side Effects of Higher Temps
The higher temperatures of the lead-free process not only require flexible temperature management, they also lead to more evaporation from solder paste, components, solder resist and PC board material. To reduce maintenance requirements for the GoReflow systems and thus to minimize costs, a flux management system with stainless steel filter is integrated into the peak and cooling area. Flux residues are collected in a PE bottle, making disposal easy and environmentally-friendly.
SEHO GoSelective light as standalone system.
Depending on the production requirements there is a choice of different conveyor arrangements available for the GoReflow systems: a belt conveyor, a chain conveyor with or without center board support, or a combination of belt and chain conveyor.
Of course, the systems are equipped with an up-to-date control unit for quick and easy programming and they may be integrated into a fully automated production line.
To eliminate costly hand soldering, in selective soldering at minimum cost is available in the GoSelective light. The system offers high quality soldering and maximum flexibility for soldering of THT components, particularly for small and medium-sized production runs. The compact, small footprint machine ensures absolutely reproducible soldering results, while providing an economical alternative to traditional hand soldering processes. The machine is designed for standalone operation with manual infeed and outfeed of the assemblies. During the process the assembly remains in its position while the working stations — the fluxer unit, preheating and soldering unit, which are mounted on a high-precision axis system — do the moving. This allows flexible processing of assemblies up to 500 x 500mm with absolutely reproducible results.
The GoSelective light uses a micro drop jet fluxer which ensures precision flux application with a precisely defined quantity of one drop. This allows a defined spray pattern with minimum overspray. Surrounding areas and components which are not meant to be soldered, will not be contaminated. The system allows the processing of all usual flux types. The preheating area is provided with halogen emitters which ideally support the evaporation of the solvent and preheating of the printed circuit boards.
The soldering unit is designed for miniwave soldering processes for a high degree of flexibility in the production line. A variety of fast change solder nozzles, suitable for dip and drag soldering processes, are available.
The solder nozzle technology used permits very small distances between the solder joints, thus it is possible to also precisely solder points which generally are difficult to get to.
Alternatively, there are two different solder nozzle types available.
Coated solder nozzles are nearly maintenance-free and they provide an almost unlimited operating lifetime. Uncoated solder nozzles may be used to process extremely small grid spacings.
Working area of the GoSelective light showing selectve solder fountain.
Local nitrogen inertion ensures an oxide-free solder wave, providing ideal flow properties of the solder. Moreover, this guarantees minimum maintenance requirements. Highest process reliability is ensured with an automatic solder wave monitoring and wave height control as well as a solder level control.
The selective soldering system has an up-to-date control unit and a high-precision axis control. The system's ease of handling meets the need for quick and effective processing. Teaching the system is particularly easy. Only the x and y coordinates of the components to be soldered have to be entered and filed with the soldering program. Of course, all soldering programs can be saved and protected via password.
For more information, contact: Seho USA, Inc., 325 L Hill Carter Parkway, Ashland, VA 23005
804-798-6000 fax: 804-798-5933 E-mail: email@example.com Web:
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